Actuating unit for a hydraulic brake system for automotive vehicles

ABSTRACT

An actuating unit for a hydraulic brake system for automotive vehicles includes a vacuum brake power booster and a master brake cylinder. To transmit the reaction forces, developing during actuation in the master brake cylinder, to a vehicle body wall which carries the actuating unit, a centrally positioned force-transmitting element is provided, which is arranged between the master brake cylinder and the vehicle body wall in terms of effect. The force-transmitting element is formed of a continuous bolt which extends in an axial direction through the control housing of the vacuum brake power booster.

BACKGROUND OF THE INVENTION

The present invention relates to an actuating unit for a hydraulic brakesystem for automotive vehicles, including a pneumatic brake powerbooster, which is preferably a vacuum brake power booster, and a masterbrake cylinder inserted after the brake power booster in terms ofeffect. The brake power booster includes a booster housing, the interiorof which is subdivided into two chambers by a movable wall which isattached to a control housing accommodating a control valve, and acentrally arranged force-transmitting element being provided which is inforce-transmitting connection with the master brake cylinder, on the onehand, and a vehicle body wall of the automotive vehicle, on the otherhand.

An actuating unit of this type is disclosed in German patent DE 29 22299. The force-transmitting element of the brake power booster of theprior-art actuating unit is provided as a carrying pipe with axialslots, through which the movable wall is coupled with a part of thecontrol housing which is arranged inside the carrying pipe and actuatesan output member transmitting the output force of the brake powerbooster.

What is considered least favorable in the referenced actuating unit isthe complicated and costly way of transmitting forces from the movablewall to the output member, which is done by means of tabs provided onthe movealble wall to the above-mentioned control housing part, in whichthe output member is held by way of a retaining ring screwed to themovable wall. For this reason, a tandem-type design would be possibleonly by very great structural efforts.

Another disadvantage is the considerable overall axial length and thecomparatively high weight of the referenced actuating unit. The highweight is mainly due to the massive carrying pipe, made of metal, andthe diaphragm plate, forming the movable walls which must be made of athick material in order to transmit major boosting forces.

Finally, still another disadvantage is that the configuration of thecarrying pipe depends on customer requests for flange patterns orvehicle-related flange patterns to mount the master brake cylinder tothe booster housing and to mount the brake power booster to the vehiclebody wall. Different carrying pipes are required for differentcombinations of flange patterns.

Therefore, an object of the present invention is to provide an actuatingunit of the previously mentioned type with a design which permitsreducing costs and weight. In addition, both the booster housing and thediaphragm plate should be made of an extremely thin sheet metal.Further, the application of control assemblies, which nowadays aretypically rated for a plurality of booster sizes, with almost allcomponent parts and in particular those requiring tools should beensured without structural modifications. Still further, the inventionis to provide a simple and inexpensive tandem-type design.

This object is achieved according to the present invention in that theforce-transmitting element is a continuous bolt which extends in anaxial direction through the control housing.

As in the past, the vacuum forces acting on the booster housing halfclosest to the vehicle body wall and the forces which are developed by apossible pulling of the actuating pedal or by an abrupt resettingmovement of the brake pedal, are introduced into the vehicle body wall.All the other occurring forces are absorbed and transmitted by thecentral bolt under pressure and tension which does not depend on thedesired flange pattern.

Due to a favorable improvement provided by the present invention, theoperating safety is increased by means of the valve piston having asleeve-shaped design. The sleeve-shaped valve piston is guided on thebolt and, with its end, supported at the actuating pedal. The preferredembodiment provides a large guide length for the valve piston so thatthe buckling risk is eliminated as far as possible.

Another embodiment of the present invention, in which the brake powerbooster includes an elastic reaction disc which is arranged in thecontrol housing and permits transmitting the output force of the brakepower booster to the piston by means of a pressure plate being inforce-transmitting connection with a piston guided in the master brakecylinder, includes a reaction disc and pressure plate that have anannular design and are positioned coaxially relative to the bolt on asleeve, which is slidably guided on the bolt. This reduces theresponse/resetting force hysteresis.

In another embodiment of the present invention, which can be produced ina particularly cost-efficient way, the output force is transmitted tothe piston by means of at least two rod-shaped elements which arearranged symmetrically in parallel to the bolt between the piston andthe pressure plate.

An improvement of the piston guide is achieved, according to anotherembodiment of the present invention, in that the output force istransmitted to the piston by means of a bolt-shaped element which isguided in a hollow-cylindrical section of the bolt having radiallyopposed slots, and which is in axial abutment against a pin positionedperpendicularly in the pressure plate. The bolt-shaped part canpreferably be formed by an axial extension of the piston.

In still another embodiment of the present invention, the end of thebolt which is associated with the master brake cylinder is connected toa closure element closing the master brake cylinder towards the outside.This allows a direct transmission of the reaction forces from the masterbrake cylinder to the vehicle body wall, without an additionaldeviation.

In the preferred embodiment of the present invention, the pneumaticforces, acting on the booster housing half closest to the master brakecylinder and depending on the vacuum, are directly transmitted to thevehicle body wall by connecting the end of the bolt associated with themaster brake cylinder to a bowl-shaped part which receives the end ofthe master brake cylinder housing projecting into the booster housingand is connected to the booster housing half closest to the mastercylinder.

The bowl-shaped part preferably has a radial collar which serves tofasten the part to the booster housing and as an abutment for aresetting spring biasing the movable wall in opposition to the actuatingdirection, so that a good guide of the resetting spring is ensured. Acost-effective simplification of the construction is provided by thebowl-shaped part being formed in one part with the booster housing halfclosest to the master cylinder.

In a further embodiment of the present invention, the torsionalstiffness of the actuating pedal is increased by the actuating pedalbeing of fork-shaped design and including two parallel arms spaced fromeach other, the bolt extending between the arms. By this means it ispossible to realize a solid actuating pedal without excess weight incomparison with conventional brake pedals.

The mounting of the actuating unit according to the present invention isconsiderably simplified because the actuating pedal is pivotallysupported at a pedal assembly mounted on the booster housing, in whichthe fastening means associated with the vehicle body wall is provided atthe periphery of the booster housing. This allows furnishing completeassemblies which can be mounted into automotive vehicles by theautomotive vehicle manufacturers without causing additional costs.

A further embodiment of the present invention provides an optimalutilization of the mounting space available in the automotive vehicle inthat the actuating unit, in the mounted condition on the vehicle bodywall, is clamped in between the booster housing and the pedal assembly.

Furthermore it is particularly preferable, when the end of the boltremote from the master brake cylinder is anchored at the pedal assembly.This is a simple way of transmitting all the forces to the vehicle bodywall through the bolt.

A shortening of the empty run occurring during actuation, which isimportant for the function, is achieved by providing a transverse memberwhich defines the inactive position of the valve piston and is in axialabutment against a ring seal sealing the booster housing towards theoutside.

Further details, characteristics and advantages of the present inventionwill become apparent to those skilled in the art from the subsequentdescription of the preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a first embodiment of the actuating unit according tothe present invention, in axial section.

FIG. 2 illustrates an embodiment of the actuating pedal which can beused with the actuating unit according to the embodiment of the presentinvention, illustrated in FIG. 1.

FIG. 3 is an illustration of selected portions of the slightly modifiedcentral part of the actuating unit according to the embodiment shown inFIG. 1, in bigger scale.

FIG. 4 illustrates a third embodiment of the actuating unit, accordingto the present invention, in an illustration corresponding to FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The actuating unit according to the present invention, as shown in FIG.1, includes a vacuum brake power booster 1 and a master brake cylinder2, which is preferably a tandem-type master cylinder, inserted after thevacuum brake power booster. The vacuum brake power booster 1 includes abooster housing 3, formed by two housing halfs 20,21 connected to eachother, in which the housing half 20, represented on the left side,supports the tandem-type master cylinder 2, while the housing half 21,represented on the right side, is fastened to a vehicle body wall 45 ofan automotive vehicle with fastening means 27,28 provided at itsperiphery.

In a cylindrically-formed extension of the right housing half 21, whichis not shown in detail, a control housing 8, including a control valve 9which can be actuated by an input member 4 being in axial abutmentagainst an actuating pedal 30, is slidably guided in a sliding ring seal16. On the end remote from the input member 4 the control housing 8supports a movable wall 5 which is formed by a diaphragm plate 22 and arolling diaphragm 23 being in abutment against it. Moveable wall 5subdivides the interior of the brake power booster housing 3 into anevacuable vacuum chamber 6 and a working chamber 7. Control valve 9permits a connection between the working chamber 7 and the vacuumchamber 6 or the atmosphere. As can be seen (especially from FIG. 3) thecontrol valve 9 is preferably formed by two sealing seats 10,11 whichhave an annular design, are arranged coaxially to each other andinteract with an elastic, rotationally symmetrical valve body 12. Valvebody 12 can be a disc valve, for example. Sealing seats 10, 11 are inabutment against valve body 12 when the vacuum brake power booster 1 isin a release position.

The first sealing seat 10, the opening of which allows a connectionbetween the two chambers 6,7, is provided in the control housing 8. Thesecond sealing seat 11, the opening of which allows a ventilation of theworking chamber 7, is provided on a valve piston 15. Valve piston 15 isguided on a continuous and centrally positioned force-transmitting bolt14 and is in force-transmitting connection with the input member 4.Valve piston 15 has a resetting movement which is limited by atransverse member 17 being, in a release position, in axial abutmentagainst a sliding ring seal. The sleeve-shaped valve piston 15 is inforce-transmitting connection with an elastic reaction disc 13, whichpreferably has an annular design. Valve piston 15 is positioned in acylindrical recess of the control housing 8 and allows the transmissionof the actuating force introduced at the input member 4, on the onehand, and also of the boosting force generated by the movable wall 5onto a pressure plate 26, on the other hand, which interacts with amaster brake cylinder piston 29.

The force-transmitting bolt 14, which preferably extends axially throughthe control housing 8, is screwed in a closure element 38 with the endclosest to the tandem-type master cylinder 2. Closure element 38 closesthe tandem-type master cylinder 2 and is fastened to the left boosterhousing half 20 by means of fastening screws 24, towards the outside.The other end of the force-transmitting bolt 14 is anchored to the pedalassembly 44. Actuating pedal 30 is pivotally supported on pedal assembly44. Pedal assembly 44 is fastened to the booster housing half 21(illustrated on the right side of the drawing) by means of the mountingelement 31,32, so that actuating pedal 30 causes a transmission of thereaction forces resulting from the pressure generated in the tandem-typemaster cylinder 2 directly from the master cylinder 2 to the vehiclebody wall 45.

Referring now to FIGS. 2 and 3, the force-transmitting bolt 14 extendsthrough the range of action of the actuating pedal 30 between twoparallel arms 42,43 of the actuating pedal 30 arms 42, 43 are spacedfrom each other, while the reaction disc 13 and the pressure plate 26are arranged on a tubular sleeve 25, which is guided slidingly on theforce-transmitting bolt 14 and receives a seal ring 48 in its radialenlarged portion 47. Certainly the actuating pedal can be designed inanother way, as for example a pedal with an opening that receives theforce-transmitting bolt 14 or a pedal with a flat arm interacting with aslotted force-transmitting bolt. In the embodiment of FIG. 3 the outputforce of the vacuum brake power booster 1 to the tandem-type mastercylinder piston 29 is transmitted by two rod-shaped elements 18,19,which are arranged symmetrically in parallel to the force-transmittingbolt 14 between the tandem-type master cylinder piston 29 and thepressure plate 26.

In the embodiment of the present invention illustrated in FIG. 3, theend of the force-transmitting bolt 14 closest to the master cylinder 2is screwed in a bowl-shaped part 40, which is screwed to the boosterhousing half 20 by means of the fastening screws 24, which fasten themaster cylinder 2 to the booster housing half 20. To this end thebowl-shaped part 40 is provided with a radial collar 41 which serves asan abutment for a resetting spring 39 biasing the movable wall 5 inopposition to the actuating direction. Alternatively, force-transmittingbolt 14 and the part 40 can be connected also in other ways, as, forexample, a connection by way of indentation, a bayonet connection andthe like. A one-piece version of the bowl-shaped part 40 with thebooster housing half 20 closest to the master cylinder is also possible.

In the embodiment of the present invention that is illustrated in FIG.4, the actuating unit 1,2 is fastened to the vehicle body wall 45 bymeans of the mounting elements 31,32, which retain the pedal assembly44. The vehicle body wall 45 is clamped in between the right boosterhousing half 21 and the pedal assembly 44. The force-transmitting bolt14 has a hollow-cylindrical section 34 which protrudes from the controlhousing 8 and provides, in the illustrated section, two radially opposedaxial slots 35,36. This embodiment provides that the output force of thevacuum brake power booster 1 is transmitted to the tandem-type mastercylinder piston 29 by means of a bolt-shaped element 33 which is formed,in the illustrated example, by an axial extension of the master cylinderpiston 29. The part 33, which is guided in the section 34 of theforce-transmitting bolt 14, is in axial abutment against a transversepin 37 guided in the slots 35,36 and positioned perpendicularly in acylindrical projection 49 of the pressure plate 26, so that the twoparts 33,37 are in a force-transmitting connection. Experts working inthe relevant field are familiar with the function of the actuating unit1,2 according to this invention which therefore does not have to bediscussed in detail.

The preceding description is exemplary rather than limiting in nature.The purview and scope of this invention is to be limited only by theappended claims.

I claim:
 1. An actuating unit for a hydraulic brake system forautomotive vehicles comprising:a pneumatic brake power booster; a masterbrake cylinder having a housing inserted after said brake power boosterin terms of effect, said brake power booster including a boosterhousing, the interior of which is subdivided into two chambers by amovable wall which is attached to a control housing accommodating acontrol valve; and a centrally arranged force-transmitting element whichis in force-transmitting connection with said master brake cylinder, onthe one hand, and a vehicle body wall of the automotive vehicle, on theother hand, said force-transmitting element being formed of a continuousbolt which extends in an axial direction through the control housing. 2.An actuating unit as claimed in claim 1, wherein said control valve ofsaid brake power booster is operable by a valve piston which interactswith an actuating pedal, and wherein said valve piston has asleeve-shaped design which is guided on said bolt and at one end, issupported at said actuating pedal.
 3. An actuating unit as claimed inclaim 2, wherein said brake power booster includes an elastic reactiondisc which is arranged in said control housing and permits transmittingan output force of said brake power booster to said piston by a pressureplate that is in force-transmitting connection with a second pistonguided in the master brake cylinder, said reaction disc and saidpressure plate having an annular design and being positioned coaxiallyrelative to said bolt on a sleeve which is slidably guided on said bolt.4. An actuating unit as claimed in claim 3, wherein said output force istransmitted to said second piston by at least two rod-shaped elementswhich are arranged symmetrically in parallel to said bolt between saidsecond piston and said pressure plate.
 5. An actuating unit as claimedin claim 3, wherein said output force is transmitted to said secondpiston by a bolt-shaped element, which is guided in a hollow-cylindricalsection of said bolt having radially opposed slots, and which is inaxial abutment against a pin positioned perpendicularly in said pressureplate.
 6. An actuating unit as claimed in claim 1, wherein one end ofsaid bolt, which is associated with said master brake cylinder, isconnected with a closure element closing said master brake cylinder. 7.An actuating unit as claimed in claim 1, wherein one end of said boltassociated with said master brake cylinder is connected to a bowl-shapedpart, one end of said master brake cylinder housing projecting into saidbooster housing and being connected to a booster housing half proximatesaid master cylinder.
 8. An actuating unit as claimed in claim 7,wherein said bowl-shaped part has a radial collar which serves to fastensaid part to said booster housing, said radial collar providing anabutment for a resetting spring for biasing said movable wall inopposition to an actuating direction.
 9. An actuating unit as claimed inclaim 7, wherein said bowl-shaped part is formed in one part with saidbooster housing half proximate said master cylinder.
 10. An actuatingunit as claimed in claim 1, further comprising an actuating pedal thatis fork-shaped and includes two parallel arms spaced from each other,said bolt extending between said arms.
 11. An actuating unit as claimedin claim 10, wherein said actuating pedal is pivotally supported at apedal assembly mounted on said booster housing.
 12. An actuating unit asclaimed in claim 11, further comprising a fastening means associatedwith a vehicle body wall provided at a periphery of said boosterhousing.
 13. An actuating unit as claimed in claim 11, wherein an end ofsaid bolt remote from said master brake cylinder is anchored at saidpedal assembly.
 14. An actuating unit as claimed in claim 1, furthercomprising a transverse member that defines an inactive position of saidvalve piston and is in axial abutment against a ring seal sealing saidbooster housing towards an outside of said booster housing.
 15. Anactuating unit for a vehicle brake system, comprising:a vacuum brakepower booster having a booster housing that includes two housing halves,at least one of said booster housing halves being coupled to a vehiclebody wall; a master brake cylinder coupled to one of said boosterhousing halves; a moveable wall disposed within said booster housing fordividing said booster housing into two chambers, said moveable wallbeing attached to a control housing, said control housing accommodatinga control valve; and a bolt directly coupled to a portion of said mastercylinder at a first bolt end and effectively coupled to said vehiclebody wall at a second bolt end, said bolt being disposed within saidbooster housing and serving to transmit forces developed in said mastercylinder during brake actuation to said vehicle body wall, furtherincluding an actuating pedal for actuating the brake system, and a valvepiston for actuating said control valve, said pedal being coupled tosaid valve piston proximate a first pedal end, said first pedal endhaving two generally parallel fork arms that receive a portion of saidbolt between said arms.
 16. The actuating unit of claim 15, furthercomprising a bowl-shaped part connected to one of said booster housinghalves, said bowl-shaped part having a radial collar for coupling saidbowl-shaped part to said booster housing half, said radial collarfurther providing an abutment surface for a biasing means that biasessaid moveable wall in a direction opposing an actuation direction. 17.An actuating unit for a vehicle brake system, comprising:a vacuum brakepower booster having a booster housing that includes two housing halves,at least one of said booster housing halves being coupled to a vehiclebody wall; a master brake cylinder coupled to one of said boosterhousing halves; a moveable wall disposed within said booster housing fordividing said booster housing into two chambers, said moveable wallbeing attached to a control housing, said control housing accommodatinga control valve; and a bolt directly coupled to a portion of said mastercylinder at a first bolt end and effectively coupled to said vehiclebody wall at a second bolt end, said bolt being disposed within saidbooster housing and serving to transmit forces developed in said mastercylinder during brake actuation to said vehicle body wall, furtherincluding an actuating pedal and wherein said control valve is operableby a valve piston having a sleeve-shaped design, said valve piston beingguided on said bolt and being supported by said pedal at one end of saidpiston, said piston interacting with said pedal to operate said controlvalve.